Stirling cooler

ABSTRACT

A Stirling cooler includes a Stirling refrigerator having a heat dissipation unit and a heat absorption unit, a cooling compartment cooled by cold heat of the heat absorption unit, a secondary refrigerant circulation circuit cooling the heat dissipation unit, and a tertiary refrigerant circulation circuit exchanging heat with the secondary refrigerant circulation circuit.

TECHNICAL FIELD

The present invention relates to a Stirling cooler, and particularly to a Stirling cooler effectively using heat of a heat dissipation unit of a Stirling refrigerator in order to, for example, prevent condensation and evaporate defrost water.

BACKGROUND ART

Japanese Patent Laying-Open No. 2003-050073 for example discloses that heat exchange in a reverse Stirling cycle is applied to a cooler.

The cooler includes a high temperature unit for dissipating to the outside compression heat of working gas in the reverse Stirling cycle, a low temperature unit for absorbing from the outside expansion heat of the working gas in the reverse Stirling cycle, and a low temperature circulation circuit configured with a closed circuit having a low temperature condenser thermally coupled to the low temperature unit and a plurality of low temperature evaporators that are coupled to each other to form a thermosiphon, and a Stirling refrigerating system is disclosed that is characterized in that a cold heat transfer medium transferring cold heat of the low temperature unit is enclosed in the low temperature circulation circuit. Here, the heat of the high temperature unit is dissipated by a high temperature heat exchange cycle (heat dissipation system). The high temperature heat exchange cycle includes a high temperature evaporator and a high temperature condenser connected by a pipe, and the heat is transferred and dissipated according to principles of the thermosiphon.

Patent Document 1: Japanese Patent Laying-Open No. 2003-050073 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The above-described heat dissipation system, however, encounters the following problems.

In the heat dissipation system, a forced circulation circuit is formed in some cases including a circulation pump in addition to the above-described thermosiphon circuit and supplied with a liquefied refrigerant from the high temperature evaporator. The heat of the refrigerant flowing in the forced circulation circuit is used for example to prevent condensation of the cooler.

Here, the pipe of the forced circulation circuit is supplied with the liquefied refrigerant of a relatively high temperature from the high temperature evaporator. Therefore, air bubbles are likely to generate in the refrigerant flowing in the pipe, which is likely to cause cavitation. The occurrence of cavitation leads to the problems that noise could be generated and the pipe could be damaged for example.

The present invention is made in view of the above-described problems. An object of the present invention is to restrain occurrence of cavitation in the pump where a tertiary refrigerant is forcefully circulated and to, for example, adequately prevent condensation using a tertiary refrigerant circulation circuit.

Means for Solving the Problems

According to an aspect, the present invention includes: a Stirling refrigerator having a heat dissipation unit and a heat absorption unit; a cooling compartment cooled by cold heat of the heat absorption unit; a secondary refrigerant circulation circuit cooling the heat dissipation unit; and a tertiary refrigerant circulation circuit exchanging heat with the secondary refrigerant circulation circuit. Preferably, a circulation pump is further included that conveys a tertiary refrigerant having exchanged heat with a secondary refrigerant of the secondary refrigerant circulation circuit to an object to be heated. Preferably, the object to be heated includes at least one of an opening of the Stirling cooler and a drain water heating unit. Preferably, the tertiary refrigerant circulation circuit has its internal pressure set at or higher than atmospheric pressure. Preferably, the secondary refrigerant circulation circuit includes an evaporator cooling the heat dissipation unit, a heat exchanger exchanging heat between the secondary refrigerant and the tertiary refrigerant, and a condenser cooling the secondary refrigerant, and the heat exchanger is disposed downstream of the evaporator with respect to direction in which the secondary refrigerant flows, and the condenser is disposed further downstream thereof. Preferably, heat exchange between the secondary refrigerant circulation circuit and the tertiary refrigerant circulation circuit is performed by a dual pipe heat exchanger. Further, preferably the secondary refrigerant and the tertiary refrigerant flow in respective directions opposite to each other in the dual pipe heat exchanger. An evaporator evaporating the secondary refrigerant and cooling the heat dissipation unit is further included, and the heat exchanger is disposed in the evaporator.

EFFECTS OF THE INVENTION

In accordance with the present invention, the tertiary refrigerant circulation circuit where the tertiary refrigerant circulates is a circulation circuit independent of the secondary refrigerant circulation circuit connected to the high temperature evaporator. Therefore, occurrence of cavitation in the pump forcefully circulating the tertiary refrigerant can be restrained and, for example, condensation can be adequately prevented by means of the forced circulation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a schematic configuration of a Stirling cooler according to a first embodiment of the present invention.

FIG. 2 is a pipe system diagram of the Stirling cooler according to the first embodiment.

FIG. 3 is a perspective view of a Stirling cooler according to a second embodiment.

FIG. 4 is a rear view of the Stirling cooler shown in FIG. 3.

FIG. 5 is a side cross-sectional view of the Stirling cooler shown in FIG. 3.

FIG. 6 is a pipe system diagram of a Stirling cooler according to a third embodiment.

FIG. 7 is a pipe system diagram of a Stirling cooler according to a fourth embodiment.

FIG. 8 is a perspective view of a heat dissipation unit and therearound of a Stirling cooler according to a fifth embodiment.

FIG. 9 is a perspective view of a heat dissipation unit and therearound of a Stirling cooler according to a sixth embodiment.

FIG. 10 is a circuit diagram showing a schematic configuration of a Stirling cooler according to a seventh embodiment.

FIG. 11 is a plan view showing another example of a heat exchanger.

FIG. 12 is a plan view showing still another example of the heat exchanger.

DESCRIPTION OF THE REFERENCE SIGNS

10 refrigerator compartment (cooling compartment), 11 freezer compartment (cooling compartment), 13 Stirling refrigerator, 13 a heat dissipation unit, 13 b heat absorption unit, 14 secondary refrigerant circulation circuit, 15 evaporator, 17 piezoelectric pump (circulation pump), 16 heat exchanger, 19 a-19 c, 20 a-20 d condensation prevention pipe, 21 drain water heating unit

BEST MODES FOR CARRYING OUT THE INVENTION

With reference to FIGS. 1 to 9, embodiments of the present invention will be described.

First Embodiment

FIG. 1 is a perspective view showing a schematic configuration of a Stirling cooler 100 according to a first embodiment of the present invention. As shown in FIG. 1, Stirling cooler 100 includes a refrigerator compartment (cooling compartment) 10 housing what is to be refrigerated (what is to be cooled), a freezer compartment (cooling compartment) 11 housing what is to be frozen (what is to be cooled) and disposed in the lower stage of refrigerator compartment 10, a cabinet (partition wall) 12 separating freezer compartment 11 and refrigerator compartment 10 from each other and made of a heat insulator, and a Stirling refrigerator 13 including a heat dissipation unit 13 a and a heat absorption unit 13 b. Stirling cooler 100 further includes a secondary refrigerant circulation circuit 14 where a heating medium (secondary refrigerant) A naturally circulates, an evaporator 15 where heating medium A evaporates to cool heat dissipation unit 13 a, a tertiary refrigerant circulation circuit 28 where a heating medium (tertiary refrigerant) B is forcefully circulated, a heat exchanger 16, and a piezoelectric pump (circulation pump) 17 forcefully circulating heating medium B. Stirling cooler 100 further includes a drain pan (reservoir) 18 storing drain water generated as a result of defrosting and disposed on the bottom side of Stirling cooler 100. Stirling refrigerator 13, heat exchanger 16 and a condenser 34 are disposed in a machine chamber 35 disposed at a substantially central portion of Stirling cooler 100. Heat exchanger 16 is disposed above Stirling refrigerator 13 and condenser 34 is also disposed above Stirling refrigerator 13.

As shown in FIG. 1, secondary refrigerant circulation circuit 14 includes a gas pipe 30 that connects the upper end of evaporator 15 and the upper surface of heat exchanger 16 and that is a place where gaseous heating medium A generated in evaporator 15 flows, and a liquid pipe 33 that connects the lower surface of heat exchanger 16 and the lower end of evaporator 15 and that is a place where heating medium A condensed in heat exchanger 16 flows. Secondary refrigerant circulation circuit 14 also includes a gas pipe 32 that connects the upper end of evaporator 15 and the upper surface of condenser 34 and that is a place where gaseous heating medium A generated in evaporator 15 flows, a liquid pipe 31 connecting the lower end of evaporator 15 and the lower surface of condenser 34, heat exchanger 16, and condenser 34.

Heating medium A circulating in secondary refrigerant circulation circuit 14 and heating medium B circulating in tertiary refrigerant circulation circuit 28 are each water or a liquid mixture of water and alcohol so that the medium is less prone to freeze. Further, the inside of secondary refrigerant circulation circuit 14 has its pressure set lower than atmospheric pressure so that heating medium A is readily evaporated in evaporator 15 at the temperature of heat dissipation unit 13 a.

Tertiary refrigerant circulation circuit 28 includes a high temperature pipe 27 connecting the lower surface of heat exchanger 16 and piezoelectric pump 17 and extending downward, a drain water heating unit 21 heating drain water in drain pan 18, condensation prevention pipes 19 a-19 c and 20 a-20 d, and a low temperature pipe 26. Tertiary refrigerant circulation circuit 28 further includes heat exchanger 16 disposed above Stirling refrigerator 13.

Piezoelectric pump 17 is disposed on the rear side of Stirling cooler 100 and drain water heating unit 21 is disposed downstream. Drain water heating unit 21 is disposed on the bottom side of Stirling cooler 100. Drain water heating unit 21 is disposed in meandering form at the lower surface of Stirling cooler 100.

Condensation prevention pipe 19 a is disposed downstream of drain water heating unit 21. Condensation prevention pipe 19 a is disposed at a side portion of a front opening of freezer compartment 11 and extends from the bottom surface of Stirling cooler 100 toward the upper surface. Condensation prevention pipe 20 a is disposed downstream of condensation prevention pipe 19 a. Condensation prevention pipe 20 a is disposed at a side portion of a front opening of refrigerator compartment 10 and extends from a substantially central portion of Stirling cooler 100 toward the upper surface. Condensation prevention pipe 20 b is disposed downstream of condensation prevention pipe 20 a. Condensation prevention pipe 20 b is disposed at the upper side portion of the front opening of refrigerator compartment 10, and condensation prevention pipe 20 c is disposed downstream of condensation prevention pipe 20 b. Condensation prevention pipe 20 c is disposed opposite to condensation prevention pipe 20 a and is disposed at a side portion of the front opening of freezer compartment 10. Condensation prevention pipe 20 d is disposed downstream of condensation prevention pipe 20 c. Condensation prevention pipe 20 d is disposed at the lower side portion of the front opening of refrigerator compartment 10, and condensation prevention pipe 19 b is disposed downstream of condensation prevention pipe 20 d. Condensation prevention pipe 19 b is disposed at the upper side portion of the front opening of freezer compartment 11 and condensation prevention pipe 19 c is disposed downstream of condensation prevention pipe 19 b. Condensation prevention pipe 19 c is disposed opposite to condensation prevention pipe 19 a and is disposed at a side portion of the front opening of freezer compartment 11.

In other words, in the present embodiment, what is to be heated by tertiary refrigerant circulation circuit 28 is the upper surface of drain pan 18 and the door packing contact portion that is the front opening of refrigerator compartment 10 and freezer compartment 11. Low temperature pipe 26 is disposed downstream of condensation prevention pipe 19 c. Low temperature pipe 26 extends from the lower side of the front opening of freezer compartment 11 toward the rear surface of Stirling cooler 100 and extends from the bottom surface of Stirling cooler 100 toward the upper surface of Stirling cooler 100. The upper end of low temperature pipe 26 is connected to the upper surface of heat exchanger 16.

The internal pressure of tertiary refrigerant circulation circuit 28 is set at or higher than atmospheric pressure. For example, it is set at 1013 hPa or higher.

FIG. 2 is a pipe system diagram of Stirling cooler 100 according to the first embodiment. As shown in FIG. 2, Stirling cooler 100 has a primary refrigerant circulation circuit 44 including a low temperature condenser 42 provided at heat absorption unit 13 b generating cold heat, a cooling unit 40 and a pipe 43 where a heating medium C circulates between low temperature condenser 42 and cooling unit 40. In the vicinity of cooling unit 40, a fan 41 is provided that supplies cold air generated by cooling unit 40 to the freezer compartment and refrigerator compartment.

Heat exchanger 16 has a hollow structure and the inside thereof is filled with heating medium B and a non-oxidizing gas. The non-oxidizing gas (non-oxidizing ambient) filling the inside of heat exchanger 16 is, for example, such a gas as nitrogen, methane and ethane. The non-oxidizing gas is not limited to these gases and may be any gas that is less prone to oxidize and rust the wall surface of heat exchanger 16. In heat exchanger 16, the pipe of secondary refrigerant circulation circuit 14 is disposed in meandering form. Therefore, a large area for heat exchange between heating medium A and heating medium B is ensured.

In Stirling cooler 100 configured as described above and shown in FIG. 1, heating medium A is first evaporated at the temperature of heat dissipation unit 13 a in evaporator 15. At this time, since the internal pressure of secondary refrigerant circulation circuit 14 is set lower than atmospheric pressure, heating medium A is adequately evaporated and heat dissipation unit 13 a is adequately cooled. Gaseous heating medium A flows through gas pipe 30 or gas pipe 32 and is supplied to condenser 34 or heat exchanger 16. Gaseous heating medium A supplied to condenser 34 is cooled and changed into liquid form in condenser 34, and flows in liquid pipe 31 and is returned into evaporator 15. Gaseous heating medium A supplied into heat exchanger 16 is cooled by heat exchange with heating medium B and is changed into liquid form, flows through liquid pipe 33 and is returned into evaporator 15. In other words, beating medium A naturally circulates in secondary refrigerant circulation circuit 14.

Heating medium B is heated by heating medium A in heat exchanger 16. At this time, since the internal pressure of tertiary refrigerant circulation circuit 28 where heating medium B flows is set equal to or higher than atmospheric pressure, heating medium B is less prone to evaporate and heating medium B in gaseous form is less prone to be generated in tertiary refrigerant circulation circuit 28. Heating medium B heated in heat exchanger 16 and thus has a high temperature flows in high temperature pipe 27 and is discharged by piezoelectric pump 17.

Heating medium B discharged by piezoelectric pump 17 to drain water heating unit 21 first heats to evaporate the drain water stored in drain pan 18. Heating medium B then flows in condensation prevention pipes 19 a to 19 c and 20 a to 20 d to heat the door packing contact portion and therearound of refrigerator compartment 10 and freezer compartment 11 (what is to be heated) and thereby restrain occurrence of condensation. Heating medium B then flows in low temperature pipe 26 to be returned into heat exchanger 16. In this way, heating medium B is forcefully circulated in tertiary refrigerant circulation circuit 28 by piezoelectric pump 17.

In Stirling cooler 100 as described above, secondary refrigerant circulation circuit 14 communicating with evaporator 15 and tertiary refrigerant circulation circuit 28 are separately and independently configured so that mutual influences are made small. Since the internal pressure of tertiary refrigerant circulation circuit 28 is set equal to or higher than atmospheric pressure, gaseous heating medium B is less prone to be generated in tertiary refrigerant circulation circuit 28. In other words, since tertiary refrigerant circulation circuit 28 does not communicate with evaporator 15, gaseous heating medium B is less prone to be generated. Further, since the internal pressure of tertiary refrigerant circulation circuit 28 is set equal to or higher than atmospheric pressure, heating medium B flowing therein is less prone to become gaseous. Therefore, gaseous heating medium B is less prone to be supplied into piezoelectric pump 17 and occurrence of cavitation can be restrained.

In addition, since the internal pressure of tertiary refrigerant circulation circuit 28 is set equal to or higher than atmospheric pressure, air babbles are less prone to become large even if air bubbles are formed in the piezoelectric element, so that the piezoelectric element can be adequately oscillated and the operation efficiency of piezoelectric pump 17 can be ensured. Moreover, since heating medium A in secondary refrigerant circulation circuit 14 is also cooled in heat exchanger 16, condenser 34 can be configured to be compact. Furthermore, the air filling the inside of heat exchanger 16 compresses for example to restrain an excessive pressure exerted on the pipe of tertiary refrigerant circulation circuit 28. Since the air filling the inside of heat exchanger 16 compresses or expands, heating medium B can stably circulate in tertiary refrigerant circulation circuit 28 and thus Stirling refrigerator 100 can be operated stably.

Second Embodiment

Referring to FIGS. 3 to 5, a second embodiment of the present invention will be described. FIG. 3 is a perspective view of a Stirling cooler 200 according to the second embodiment. As shown in FIG. 3, a heat exchanger 51 and a condenser 52 are disposed on the rear side of Stirling cooler 200. A suction tank 53 is disposed at one of the side portions of the rear side of Stirling cooler 200. Suction tank 53 is structured in columnar form and extends from the upper surface toward the lower surface of Stirling cooler 200 and is embedded in a cabinet 12 formed of a heat insulator.

The diameter of suction tank 53 is made larger than that of a high temperature pipe 27 for example connected to the upper end of suction tank 53. The lower end of suction tank 53 is located at the bottom surface of Stirling cooler 200. The lower end of suction tank 53 is connected to a piezoelectric pump 17. The inside of suction tank 53 is filled with a non-oxidizing gas. A drain water heating unit 21 and condensation prevention pipes 19 a-19 c and 20 a-20 d are connected downstream of piezoelectric pump 17. A low temperature pipe 26 is connected most downstream thereof. Low temperature pipe 26 is connected to the lower end of heat exchanger 51.

Heat exchanger 51 is formed in the shape of a flat plate and is disposed to extend in the up and down direction on the rear surface side of Stirling cooler 200. Heat exchanger 51 includes a gas pipe 30 connected to the upper end of an evaporator 15 and a liquid pipe 33 connected to the lower end of evaporator 15.

Condenser 52 includes a pair of head pipes 52 a, 52 a disposed separate from each other and a parallel pipe 52 b disposed between head pipes 52 a, 52 a to connect head pipes 52 a, 52 a to each other. In other words, condenser 52 is also formed in the shape of a flat plate like heat exchanger 51. Of the paired head pipes 52 a, the lower end of one head pipe 52 a is connected to gas pipe 30 while the lower end of the other head pipe 52 a is connected to liquid pipe 31. Liquid pipe 31 is connected to evaporator 15. Between head pipes 52 a, 52 a, a plurality of parallel pipes 52 b are disposed at regular intervals.

FIG. 4 is a rear view of Stirling cooler 200 according to the second embodiment. As shown in FIG. 4, heat exchanger 51 and condenser 52 are both disposed above a Stirling refrigerator 13. At parallel pipe 52 b of condenser 52, a plurality of heat dissipation fins 52 c are disposed. FIG. 5 is a side cross-sectional view of Stirling cooler 200 according to the second embodiment. As shown in FIG. 5, around heat exchanger 51 and condenser 52 shown in FIG. 4, a duct 54 is disposed. Duct 54 is disposed to surround at least the periphery of heat exchanger 51, and extends in the up and down direction from the bottom surface side toward the upper surface side of Stirling cooler 200.

Namely, duct 54 extends in the up and down direction and heat exchanger 51 shown in FIG. 4 also extends in the up and down direction along duct 54. Therefore, heat exchanger 51 and duct 54 are disposed both to extend in the up and down direction and heat exchanger 51 is disposed to extend along duct 54. Near the upper end of duct 54, a fan 55 is disposed. Elements and features except for the above-described ones are similar to those of the first embodiment, and like elements are denoted by like reference characters.

In Stirling cooler 200 configured as described above, heating medium A heated in evaporator 15 circulates in heat exchanger 51 and condenser 52. Therefore, the air around heat exchanger 51 and condenser 52 is heated. Since duct 54 is disposed around heat exchanger 51 and condenser 52, airflow is generated in duct 54 and the air flows from the bottom portion toward the top portion of duct 54. In addition, since fan 55 draws the air in duct 54 toward the outside, the airflow from the bottom portion toward the top portion in duct 54 is adequately generated in duct 54. The airflow generated in duct 54 then cools heat exchanger 51 and condenser 52.

Heating medium A flowing in condenser 52 flows through head pipe 52 a and in parallel pipe 52 b. Here, a plurality of parallel pipes 52 b are disposed, and thus the area where the air flowing in parallel pipes 52 b and the air flowing in duct 54 contact each other is large, and heating medium A flowing in parallel pipes 52 b is cooled. Since a plurality of heat dissipation fins 52 c are provided at parallel pipes 52 b, heating medium A flowing in parallel pipes 52 b is adequately cooled. Since suction tank 53 is embedded in cabinet 12, the temperature of heating medium B in suction tank 53 is prevented from being dissipated to the outside.

Regarding Stirling cooler 200 in the present embodiment, heat exchanger 51 and condenser 52 are formed in the shape of a flat plate. Therefore, they can be disposed on the rear side of Stirling cooler 200. Since suction tank 53 is formed in the shape of a column and disposed on the rear side of Stirling cooler 200, the size of a machine chamber 35 can be made compact and the appropriate size of refrigerator compartment 10 and freezer compartment 11 can be ensured.

Duct 54 is disposed around heat exchanger 51 and condenser 52 and fans 55 are driven so that airflow can be generated adequately in duct 54 and heating medium A flowing in condenser 52 and heat exchanger 51 can be cooled.

A plurality of parallel pipes 52 b where heating medium A flows are provided in condenser 52 and a plurality of heat dissipation fins 52 c are provided at parallel pipes 52 b, so that heating medium A flowing in condenser 52 can be cooled adequately and condenser 52 can be made compact.

Suction tank 53 filled with a gas is provided in tertiary refrigerant circulation circuit 28 so that heating medium B can be flown stably by compression or expansion of the gas in suction tank 53 even if the volume of heating medium B changes in tertiary refrigerant circulation circuit 28 or fluctuation of flowing heating medium B occurs.

In addition, since secondary refrigerant circulation circuit 14 and tertiary refrigerant circulation circuit 28 are configured separately and independently like those of the first embodiment, functions and effects similar to those of the first embodiment can be obtained.

Third Embodiment

Referring to FIG. 6, a third embodiment of the present invention will be described. FIG. 6 is a pipe system diagram of a Stirling cooler 300 according to a third embodiment. As shown in FIG. 6, an evaporator 15 is provided with a dual pipe heat exchanger 80 having respective functions of the condenser and the heat exchanger disposed above evaporator 15. Dual pipe heat exchanger 80 includes an outer pipe 81 and an inner pipe 82 formed to have a smaller diameter than that of outer pipe 81 and provided in outer pipe 81. At the outer peripheral surface of outer pipe 81, a plurality of heat dissipation fins 83 are provided. Between outer pipe 81 and inner pipe 82, a secondary refrigerant circulation circuit 14 is connected, and inner pipe 82 is connected to a tertiary refrigerant circulation circuit 28. In other words, a gas pipe 30 of secondary refrigerant circulation circuit 14 is connected to the upper end of dual pipe heat exchanger 80 and between outer pipe 81 and inner pipe 82, while a liquid pipe 33 is connected to the lower end of dual pipe heat exchanger 80 and between outer pipe 81 and inner pipe 82.

Further, a high temperature pipe 27 of tertiary refrigerant circulation circuit 28 is connected to the upper end and the inner pipe 82 of dual pipe heat exchanger 80, and a low temperature pipe 26 is connected to the lower end and inner pipe 82 of dual pipe heat exchanger 80.

Therefore, between inner pipe 82 and outer pipe 81 of dual pipe heat exchanger 80, heating medium A flows, while heating medium B circulates in inner pipe 82, and respective directions in which heating medium A flows and heating medium B flows are opposite to each other. In the vicinity of dual pipe heat exchanger 80, a fan 84 is provided that blows air toward dual pipe heat exchanger 80.

In the present embodiment, heat dissipation fins 83 provided at dual pipe heat exchanger 80 and fan 84 are disposed. Instead, dual pipe heat exchanger 80 may be embedded in a cabinet without providing heat dissipation fins 83 and fan 84. Alternatively, the periphery of dual pipe heat exchanger 80 may be surrounded by a duct.

In Stirling cooler 300 thus configured, gaseous heating medium A generated in evaporator 15 is supplied from the upper end of dual pipe heat exchanger 80 into dual pipe heat exchanger 80. Here, since dual pipe heat exchanger 80 is disposed above evaporator 15, gaseous heating medium A generated in evaporator 15 is adequately supplied into dual pipe heat exchanger 80. Heating medium B is supplied from the lower end of dual pipe heat exchanger 80 into dual pipe heat exchanger 80.

Here, heat exchange occurs between heating medium B flowing in inner pipe 82 and heating medium A flowing between inner pipe 82 and outer pipe 81, so that heating medium A is cooled while heating medium B is heated. Fan 84 blows the outside air toward outer pipe 81 and a plurality of heat dissipation fins 83 are provided at outer pipe 81. Therefore, heating medium A flowing between outer pipe 81 aid inner pipe 82 is cooled. Thus, heating medium A is cooled while flowing in dual pipe heat exchanger 80 and heating medium B is heated. The heated heating medium B flows in high temperature pipe 27 and suction tank 53 and is forcefully circulated in tertiary refrigerant circulation circuit 28 by piezoelectric pump 17. Heating medium B flows in a condensation prevention pipe 19 and a drain water heating unit and is returned again into dual pipe heat exchanger 80. Heating medium A flows in dual pipe heat exchanger 80 and is thereafter returned into evaporator 15.

In the case where the periphery of dual pipe heat exchanger 80 is surrounded by a duct, the heat of heating medium A flowing between outer pipe 81 and inner pipe 82 causes an airflow in the duct. Therefore, the airflow generated in the duct cools the surface of outer pipe 81 of dual pipe heat exchanger 80.

Regarding Stirling cooler 300 in the third embodiment, dual pipe heat exchanger 80 has respective functions of heat exchanger and condenser, so that the body of Stirling cooler 300 as well as the machine chamber can be made compact. Therefore, an appropriate capacity of the refrigerator compartment and that of the freezer compartment can be ensured. In the case where dual pipe heat exchanger 80 is embedded in the cabinet, dual pipe heat exchanger 80 can be provided without reducing respective capacities of the refrigerator compartment and the freezer compartment formed in the cabinet. In the case where the duct is provided around dual pipe heat exchanger 80, heating medium A flowing in outer pipe 81 can be adequately cooled.

Fourth Embodiment

Referring to FIG. 7, a fourth embodiment of the present invention will be described. FIG. 7 is a pipe system diagram of a Stirling cooler in the fourth embodiment. As shown in FIG. 7, Stirling cooler 400 in the present embodiment includes a dual pipe heat exchanger 90 provided above an evaporator 15, a pipe 93 and a plurality of heat dissipation fins 93 a provided at the surface of pipe 93.

Evaporator 15 is provided with a gas pipe 94 extending upward. To a connection unit 94 a formed at the upper end of gas pipe 94, dual pipe heat exchanger 90 and pipe 93 are connected. Dual pipe heat exchanger 90 includes an outer pipe 91 and an inner pipe 92 formed to have a smaller diameter than that of outer pipe 91 and provided in outer pipe 91. Between outer pipe 91 and inner pipe 92, a secondary refrigerant circulation circuit 14 is connected. To inner pipe 92, a tertiary refrigerant circulation circuit 28 is connected.

At the lower end of dual pipe heat exchanger 90, a connection unit 90 a is provided. To connection unit 90 a, a liquid pipe 96 connected between outer pipe 91 and inner pipe 92 and a low temperature pipe 26 supplying heating medium B into inner pipe 92 are connected.

In Stirling cooler 400 configured as described above, gaseous heating medium A generated in evaporator 15 flows in gas pipe 94 to the upper portion. Gaseous heating medium A at connection unit 94 a enters the part between outer pipe 91 and inner pipe 92 of dual pipe heat exchanger 90 and enters pipe 93.

From low temperature pipe 26 connected to connection unit 90 a, heating medium B at a low temperature is supplied into dual pipe heat exchanger 90. Therefore, heat exchange occurs between heating medium A and heating medium B in dual pipe heat exchanger 90. In this way, heating medium A is cooled. Further, heating medium A flowing in pipe 93 is cooled while flowing in pipe 93 by dissipating heat to the outside. Here, since pipe 93 is provided with a plurality of heat dissipation fins 93 a, heating medium A is adequately cooled. Thus, heating medium A is cooled not only in pipe 93 but also in dual pipe heat exchanger 90 so that it is unnecessary to provide many heat dissipation fins 93 a at pipe 93 and a large space can be provided between heat dissipation fins 93 a.

Regarding Stirling cooler 400 in the fourth embodiment, a large space can be provided between heat dissipation fins 93 a. Therefore, the possibilities that the gap between heat dissipation fins 93 a is clogged with dust or the like can be reduced. Since the clogging with dust of the gap between heat dissipation fins 93 a can be restrained, the heat dissipation ability of pipe 93 can be kept for a long time so that heating medium A can be adequately cooled. Since Stirling cooler 400 in the fourth embodiment has dual pipe heat exchanger 90 like the third embodiment, the fourth embodiment can achieve functions and effects similar to those of the third embodiment.

Fifth Embodiment

Referring to FIG. 8, a fifth embodiment of the present invention will be described. FIG. 8 is a perspective view of a heat dissipation unit and therearound of a Stirling cooler in the fifth embodiment.

As shown in FIG. 8, a heating unit 95 communicating with a tertiary refrigerant circulation circuit 28 and an evaporator 15 are provided around heat dissipation unit 13 a of the Stirling refrigerator. Heating unit 95 is configured to have a pipe 95 a wound in spiral form around the surface of heat dissipation unit 13 a which is configured in substantially columnar shape. Pipe 95 a is disposed near or to be in contact with the surface of heat dissipation unit 13 a. Evaporator 15 is disposed around heat dissipation unit 13 a to include heat dissipation unit 13 a and heating unit 95 therein. The inside of evaporator 15 is filled with heating medium A to a level higher than the central portion. Therefore, a part of heating unit 95 is disposed to be immersed in heating medium A in evaporator 15. Heating unit 15 has one end connected to a low temperature pipe 26 and has the other end connected to a high temperature pipe 27.

Evaporator 15 is doughnut-shaped and fit on heat dissipation unit 13 a. The upper end of evaporator 15 is connected to a gas pipe 30 communicating with a condenser (not shown) and to a liquid pipe 31 where heating medium A liquefied in the condenser flows.

In the Stirling cooler thus configured, heating medium B flowing in heating unit 95 is directly heated by heat dissipation unit 13 a and is also heated by high-temperature heating medium A in evaporator 15. Therefore, while heating medium B is adequately heated, heat dissipation unit 13 a and heating medium A are cooled. Further, heating unit 95 has a part that is in contact with gaseous heating medium A and heat exchange adequately occurs between this part and gaseous heating medium A and heating medium B in heating unit 95 is adequately heated. In other words, gaseous heating medium A has a larger heat quantity than that of liquid heating medium A and therefore, heating medium B in heating unit 95 located at a higher level than the liquid level of heating medium A can receive a large quantity of heat from gaseous heating medium A. Moreover, since heating unit 95 is located near or in contact with heat dissipation unit 13 a, heating unit 95 directly receives heat from heat dissipation unit 13 a. Thus, heating medium B flowing in heating unit 95 is adequately heated.

In the Stirling cooler of the present embodiment, heating medium B is adequately heated in evaporator 15. Therefore, in the condensation prevention pipe and the drain water heating unit provided to tertiary refrigerant circulation circuit 28, occurrence of condensation and heating of the drain water can be adequately performed.

Moreover, since heat exchange between heating medium A and heating medium B is performed in evaporator 15, the heat exchanger is unnecessary, compact configuration can be achieved and respective capacities of the refrigerator compartment and the freezer compartment can be ensured.

Sixth Embodiment

Referring to FIG. 9, a sixth embodiment of the present invention will be described. FIG. 9 is a perspective view of a heat dissipation unit and therearound of a Stirling cooler in the sixth embodiment. As shown in FIG. 9, a hollow evaporator 15 divided into two portions is disposed around a heat dissipation unit 13 a of the Stirling refrigerator, and evaporator 15 includes two partial evaporator portions 15 a and 15 b. Evaporator portions 15 a and 15 b are semi-annular shaped and fit from opposing sides of heat dissipation unit 13 a. In other words, the outer arc-shaped surface on the inner diameter side of evaporator portions 15 a and 15 b and the peripheral surface of heat dissipation unit 13 a are in contact with each other. Further, the inside of evaporator portions 15 a and 15 b is filled with heating medium A to a level higher than the central portion. The upper end of evaporator portions 15 a, 15 b is connected to a gas pipe 30 communicating with a condenser (not shown) and a liquid pipe 31 where heating medium A liquefied by the condenser flows.

A heating unit 95 includes a heater portion 95 c disposed in evaporator portion 15 a and a heater portion 95 b disposed in evaporator portion 15 b. Heater portions 95 c, 95 b are semi-annular shaped. The outer surface on the inner diameter side of heater portions 95 c, 95 b is disposed at a distance from the inner surface on the inner diameter side of evaporator portions 15 a, 15 b. Therefore, the part between the surface of evaporator portions 15 a, 15 b that is in contact with the surface of heat dissipation unit 13 a and the surface on the inner diameter side of heater portions 95 c, 95 b is filled with heating medium A.

The upper end of heater portions 95 c, 95 b is located near the upper end of evaporator portions 15 a, 15 b and is located at a higher level than the liquid level of heating medium A filling the inside of evaporator portions 15 a, 15 b.

Heater portions 95 c, 95 b are connected to a low temperature pipe 26 supplying heating medium B into heater portions 95 c, 95 b and a high temperature pipe 27 discharging the heated heating medium B from the inside of heater portions 95 c, 95 b. High temperature pipe 27 is connected to heater portions 95 c, 95 b at a level higher than the liquid level of heating medium A filling the inside of evaporator portions 15 a, 15 b.

In the Stirling cooler thus configured, heating medium A filling the inside of evaporator portions 15 a, 15 b is heated by heat dissipation unit 13 a to have a high temperature, while a part of the medium is a high temperature gas. Therefore, while heating medium B in heater portion 95 b is adequately heated, beating medium A exchanging heat with heating medium B is cooled.

Further, heating medium A filling the part between the peripheral surface on the inner diameter side of heater portions 95 c, 95 b and the peripheral surface of evaporator portions 15 a, 15 b cools heat dissipation unit 13 a, while heated by heat dissipation unit 13 a to have a high temperature. Therefore, the peripheral surface on the inner diameter side of heater portions 95 c, 95 b is heated by high temperature heating medium A. Heater portions 95 c, 95 b extend to the portion near the upper end of evaporator portions 15 a, 15 b and the part near the upper end of evaporator portions 15 a, 15 b is filled with high temperature gaseous heating medium A. Therefore, the part near the upper end of heater portions 95 c, 95 b is heated by the high temperature gaseous heating medium A.

Heating medium B heated in heater portions 95 c, 95 b flows through high temperature pipe 27 and is discharged from heater portions 95 c, 95 b. At this time, the peripheral portion of high temperature pipe 27 is filled with the high temperature gaseous heating medium A and therefore, heating medium B flowing in high temperature pipe 27 is adequately heated by this gaseous heating medium A. Then, the medium circulates in tertiary refrigerant circulation circuit 28 and flows in the drain water heating unit and the condensation prevention pipe to heat the drain water and restrain occurrence of condensation. The Stirling cooler in the present embodiment provides heat exchange between heating medium A and heating medium B similarly to the fifth embodiment, and therefore, functions and effects similar to those of the fifth embodiment can be achieved.

Seventh Embodiment

FIG. 10 is a circuit diagram showing a schematic configuration of a Stirling cooler 100 according to a seventh embodiment. As shown in FIG. 10, Stirling cooler 100 includes a secondary refrigerant circulation circuit 102 where heating medium A circulates, and a tertiary refrigerant circulation circuit 101 where heating medium B circulates. Secondary refrigerant circulation circuit 102 includes an evaporator 112 cooling a heat dissipation unit 13 a of a Stirling refrigerator 13 shown in FIG. 1, a heat exchanger 103 exchanging heat with heating medium B of tertiary refrigerant circulation circuit 101, and a condenser 123 cooling heating medium A.

Heat exchanger 103 is disposed above evaporator 112 and condenser 123 is disposed above heat exchanger 103. Heating medium A circulates by flowing from evaporator 112 to and through heat exchanger 103 and flowing from heat exchanger 103 to and through condenser 123, and returning to evaporator 112. In other words, heat exchanger 103 is disposed downstream of evaporator 112 with respect to the flow direction of heating medium A, and condenser 123 is disposed downstream of heat exchanger 103 with respect to the flow direction of heating medium A.

Evaporator 112 and heat exchanger 103 are connected by a pipe 124A and heat exchanger 103 and condenser 123 are connected by a pipe 124B. A flow area L2 of heating medium A in pipe 124B is made larger than a flow area L1 of heating medium A in pipe 124A. Between the lower end of heat exchanger 103 and the evaporator, a liquid return pipe 124C for returning heating medium A liquefied in heat exchanger 103 into evaporator 112 is provided. Between condenser 123 and evaporator 112, a pipe 125 is connected. In the vicinity of condenser 123, a fan 126 for cooling condenser 123 is disposed.

Tertiary refrigerant circulation circuit 101 includes a piezoelectric pump 108 forcefully circulating heating medium B, a condensation prevention pipe 110 and a drain water heating unit 111 disposed downstream of piezoelectric pump 108 with respect to the flow direction of heating medium B, a heat exchanger 103 disposed downstream of condensation prevention pipe 110 and drain water heating unit 111 with respect to the flow direction of heating medium B, and a suction tank 105 disposed downstream of heat exchanger 103 with respect to the flow direction of heating medium B. Suction tank 105 is formed in the shape of a tube extending in the up and down direction, and in an upper end portion of suction tank 105, a gas ambient such as nitrogen is contained. In the portion from the central part to the lower end of suction tank 105, heating medium B is contained.

The position of the liquid level of heating medium B in suction tank 105 is uniquely determined by the amount of heating medium B filling the inside of tertiary refrigerant circulation circuit 101. Between suction tank 105 and heat exchanger 103, a pipe 104 is connected. An opening 104 a of pipe 104 located at suction tank 105 is disposed at the upper end portion of suction tank 105, and is exposed in the nitrogen gas ambient filling the inside of suction tank 105. Heat exchanger 103 includes a pipe 103 a where heating medium B flows and a housing 103 b that is formed to cover pipe 103 a and that is a pipe where heating medium A flows.

In Stirling cooler 100 thus configured, heating medium A is heated in evaporator 112 and a part thereof is evaporated. Gaseous heating medium A heated to a high temperature flows through pipe 124A into heat exchanger 103. In heat exchanger 103, heat exchange occurs between heating medium A and heating medium B flowing in pipe 103 a and heating medium A is thus cooled. Heating medium A liquefied by the heat exchange flows in pipe 124C and is returned into evaporator 112. Gaseous heating medium A after the heat exchange flows in pipe 124B into condenser 123 and is cooled.

As seen from the above, heat exchanger 103 and condenser 123 are successively disposed in series in the flow direction of heating medium A. Therefore, heating medium A can be flown through both of heat exchanger 103 and condenser 123 and heating medium A can be adequately cooled. Further, since flow area L2 of pipe 124B is formed larger than flow area L1 of pipe 124A, the resistance when heating medium A flows from heat exchanger 103 to condenser 123 is reduced. Thus, heating medium A is prevented from staying in heat exchanger 103 and heating medium A adequately flows toward condenser 123.

Since heat exchanger 103 is disposed upstream of condenser 123 in the flow direction of heating medium A, high temperature heating medium A can heat heating medium B so that the heat exchange efficiency can be improved. Here, if heating medium A condenses in condenser 123, the internal pressure in condenser 123 is prone to become lower than the internal pressure of heat exchanger 103. Therefore, heating medium A in heat exchanger 103 is prone to be drawn toward condenser 123, and heating medium A adequately circulates in secondary refrigerant circulation circuit 102. Heating medium A cooled to be liquefied in condenser 123 flows through pipe 125 and is supplied into evaporator 112.

Heating medium B is heated by heat exchange between heating medium A and heating medium B in heat exchanger 103. Heating medium B then flows through pipe 104 and enters suction tank 105. In suction tank 105, the gas included in heating medium B is separated. Since opening 104 a of pipe 104 is exposed in the gas ambient, no external pressure is exerted on a portion near opening 104 a. Therefore, air bubbles moving close to opening 104 a are adequately discharged into suction tank 105. Thus, air bubbles in tertiary refrigerant circulation circuit 101 are separated in suction tank 105. Heating medium B flows through pipe 107 connected to the lower end of suction tank 105 and flows toward piezoelectric pump 108.

Heating medium B is pressurized by piezoelectric pump 108 and discharged toward condensation prevention pipe 110 and drain water heating unit 111. As heating medium B flows in condensation prevention pipe 110, the door packing contact portion and therearound of the freezer compartment and the refrigerator compartment is heated and thereby occurrence of condensation is restrained. As heating medium B flows in drain water heating unit 111, the drain water is heated and evaporated. Heating medium B flowing through condensation prevention pipe 110 and drain water heating unit 111 is thereafter supplied into heat exchanger 103 and heated again.

FIG. 11 is a plan view showing another example of heat exchanger 103. Heat exchanger 103 shown in FIG. 11 includes main pipes 134, 135 disposed opposite to each other, a plurality of sub pipes 136 coupling main pipes 134, 135, and an inner pipe 132. Inner pipe 132 is bent in meandering manner so that it passes in each sub pipes 136.

In heat exchanger 103 thus configured, heating medium A heated in evaporator 112 shown in FIG. 10 is supplied from main pipe 134 into heat exchanger 103. Heating medium A flows in sub pipes 136 and flows from main pipe 135 toward condenser 123 shown in FIG. 10. Here, since heat exchanger 103 includes a plurality of sub pipes 136 where heating medium A flows, a large flow area of heating medium A is ensured. Therefore, the flow resistance of heating medium A is reduced and heating medium A adequately flows in heat exchanger 103.

Inner pipe 132 where heating medium B flows is disposed to pass in each sub pipe 136. Heat exchange between heating medium A and heating medium B occurs at the surface of inner pipe 132 in sub pipe 136 and inner pipe 132 is disposed in sub pipes 136. Therefore, a large area where the heat exchange occurs is ensured and the heat exchange efficiency can be improved. Since heating medium A adequately flows, the heat exchange efficiency between heating medium A and heating medium B can be further improved.

FIG. 12 is a plan view showing still another example of heat exchanger 103. Heat exchanger 103 includes main pipes 134, 135 disposed opposite to each other, a plurality of sub pipes 136 disposed between main pipes 134, 135, and a meandering pipe 137 disposed on the surface of sub pipes 136. Meandering pipe 137 extends in the direction in which it crosses sub pipes 136 and is turned on sub pipes 136 and thus formed in meandering manner. Therefore, a large area of contact between meandering pipe 137 and sub pipes 136 is ensured.

Heating medium A from main pipe 134 enters heat exchanger 103 white heating medium B flows in meandering pipe 137. Thus, at the surface of contact between meandering pipe 137 and sub pipes 136, heat exchange between heating medium A and heating medium B occurs. Since such heat exchanger 103 is configured by disposing meandering pipe 137 on the surface of sub pipes 136, the heat exchanger can be manufactured easily. By adjusting the shape, for example, the number of turns of meandering pipe 137, the area of contact between sub pipes 136 and meandering pipe 137 can be adjusted and the efficiency of heat exchange between heating medium A and heating medium B can be adjusted easily.

In Stirling cooler 100 thus configured, as shown in FIG. 10, heat exchanger 103 and condenser 123 are successively disposed in the flow direction of heating medium A, so that circulation of heating medium A can be ensured. Accordingly, heat dissipation unit 13 a of Stirling refrigerator 13 shown in FIG. 1 can be adequately cooled. Further, as heating medium A adequately circulates, the efficiency of heat exchange between heating medium A and heating medium B in heat exchanger 103 can be improved. Since the efficiency of heat exchange between heating medium A and heating medium B can be improved, occurrence of condensation can be adequately restrained and the drain water can be adequately vaporized.

Opening 104 a of pipe 104 is exposed in the gas ambient of suction tank 105, and thus air bubbles in tertiary refrigerant circulation circuit 101 can be adequately separated in suction tank 105.

Air bubbles are prevented from staying in tertiary refrigerant circulation circuit 101, and thus heating medium B can be adequately circulated.

While embodiments of the present invention have been described, it is also originally intended that the above-described elements of the embodiments are appropriately combined. Further, it should be construed that the embodiments herein disclosed are by way of examples and illustrations in all respects, not limitation. The scope of the present invention is indicated by claims and includes all modifications equivalent in meaning and scope to the claims.

INDUSTRIAL APPLICABILITY

The present invention is appropriate for a Stirling cooler. 

1. A Stirling cooler comprising: a Stirling refrigerator having a heat dissipation unit and a heat absorption unit; a cooling compartment cooled by cold heat of said heat absorption unit; a secondary refrigerant circulation circuit cooling said heat dissipation unit; and a tertiary refrigerant circulation circuit exchanging heat with said secondary refrigerant circulation circuit.
 2. The Stirling cooler according to claim 1, further comprising a circulation pump conveying a tertiary refrigerant having exchanged heat with a secondary refrigerant of said secondary refrigerant circulation circuit to an object to be heated.
 3. The Stirling cooler according to claim 2, wherein said object to be heated includes at least one of an opening of said Stirling cooler and a drain water heating unit.
 4. The Stirling cooler according to claim 1, wherein said tertiary refrigerant circulation circuit has its internal pressure set at or higher than atmospheric pressure.
 5. The Stirling cooler according to claim 1, wherein said secondary refrigerant circulation circuit includes an evaporator cooling said heat dissipation unit, a heat exchanger exchanging heat between said secondary refrigerant and said tertiary refrigerant, and a condenser cooling said secondary refrigerant, and said heat exchanger is disposed downstream of said evaporator with respect to direction in which said secondary refrigerant flows, and said condenser is disposed further downstream thereof.
 6. The Stirling cooler according to claim 1, wherein heat exchange between said secondary refrigerant circulation circuit and said tertiary refrigerant circulation circuit is performed by a dual pipe heat exchanger.
 7. The Stirling cooler according to claim 6, wherein said secondary refrigerant and said tertiary refrigerant flow in respective directions opposite to each other in said dual pipe heat exchanger.
 8. The Stirling cooler according to claim 1, further comprising an evaporator evaporating said secondary refrigerant and cooling said heat dissipation unit, wherein said heat exchanger is disposed in said evaporator. 